The present invention relates to an apparatus for diagnosing a fault in a hydraulic pressure source for operating a hydraulic pressure instrument.
In the gazette of Japanese Patent Publication No. 56-40058(1981) is disclosed an operation inspecting apparatus for automatically inspecting an operating condition of an antilock control device which prevent locking of wheels upon emergency braking of a motor car. This apparatus is provided with many switches such as an operation detector switch for detecting an operation of a modulator provided in an oil path for leading a braking hydraulic pressure to wheel cylinders to control a hydraulic pressure applied to the wheel cylinders, a pressure switch for detecting a fluid pressure in an accumulator which accumulates control fluid to be fed to the modulator, and a drive detector switch for detecting a driving state of an engine, and a decision circuit determines whether a fault is present or not on the basis of the states of these switches. And provision is made such that in the case where the same decision circuit has determined that a fault is present, an alarm device such as a lamp, a buzzer, or the like may operate. By means of this apparatus a fault of a hydraulic pressure source for the above-mentioned modulator can be also detected.
However, in the above-described example of the apparatus in the prior art, since a large number of detection signals from the respective switches must be subjected to complicated signal processing and then input to the decision circuit, the construction of the inspecting apparatus becomes complex, and this becomes one cause of a high cost.